t_H (clock hold time)

The length of time for which data that feeds a register via its data or enable input(s) must be retained at an input pin after the clock signal that clocks the register is asserted at the clock pin.

In the Quartus^® II software, you can specify a required t_H for the entire project and/or for any input pin, bidirectional pin, input register, or clock. You can also specify a point-to-point t_H requirement between an input pin and a register.

The Timing Analyzer calculates t_H using the following equation:

t_H = <clock to destination register delay> + <micro hold delay of destination register> - <pin to register delay>